Broken? : Yeah sometimes, you might haphazardly configured/changed your environment and that somehow broke you’r terminal
Effects : Commands like ls, cd , bash don’t work
Solution:
1. Open Terminal
2. Type PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin and press enter
3. Type export PATH and press enter
Godhc's Blog 